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Pontiac Grand Prix: Real World MPG

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Comments

  • All, came up with a spreadsheet doing a little figuring on whether it is worth additional money for better gas, from strictly a MPG cost perspective. Not from a feel/power/engine health perspective. Don't have enough mileage data on my own 06 GXP, but will monitor. Thoughts? Here is the data, assuming $2.75/gallon regular unleaded. Here is the data you can plot for yourself.

    First Column is MPG with regular Gas
    2nd Column is MPG Need if upgraded gas is 10 cents more a gallon to break even
    3rd Column is MPG Needed if gas is 20 cents more break even
    4th Column is 30 cents break even

    MPG $0.10 $0.20 $0.30
    19 19.69090909 20.38181818 21.07272727
    19.2 19.89818182 20.59636364 21.29454545
    19.4 20.10545455 20.81090909 21.51636364
    19.6 20.31272727 21.02545455 21.73818182
    19.8 20.52 21.24 21.96
    20 20.72727273 21.45454545 22.18181818
    20.2 20.93454545 21.66909091 22.40363636
    20.4 21.14181818 21.88363636 22.62545455
    20.6 21.34909091 22.09818182 22.84727273
    20.8 21.55636364 22.31272727 23.06909091
    21 21.76363636 22.52727273 23.29090909
    21.2 21.97090909 22.74181818 23.51272727
    21.4 22.17818182 22.95636364 23.73454545
    21.6 22.38545455 23.17090909 23.95636364
    21.8 22.59272727 23.38545455 24.17818182
    22 22.8 23.6 24.4
    22.2 23.00727273 23.81454545 24.62181818
    22.4 23.21454545 24.02909091 24.84363636
    22.6 23.42181818 24.24363636 25.06545455
    22.8 23.62909091 24.45818182 25.28727273
    23 23.83636364 24.67272727 25.50909091
    23.2 24.04363636 24.88727273 25.73090909
    23.4 24.25090909 25.10181818 25.95272727
    23.6 24.45818182 25.31636364 26.17454545
    23.8 24.66545455 25.53090909 26.39636364
    24 24.87272727 25.74545455 26.61818182
    24.2 25.08 25.96 26.84
    24.4 25.28727273 26.17454545 27.06181818
    24.6 25.49454545 26.38909091 27.28363636
    24.8 25.70181818 26.60363636 27.50545455
    25 25.90909091 26.81818182 27.72727273
    25.2 26.11636364 27.03272727 27.94909091
    25.4 26.32363636 27.24727273 28.17090909
    25.6 26.53090909 27.46181818 28.39272727
    25.8 26.73818182 27.67636364 28.61454545
    26 26.94545455 27.89090909 28.83636364
    26.2 27.15272727 28.10545455 29.05818182
    26.4 27.36 28.32 29.28
    26.6 27.56727273 28.53454545 29.50181818
    26.8 27.77454545 28.74909091 29.72363636
    27 27.98181818 28.96363636 29.94545455

  • All,
    Just finished the first segment of a road trip. Here are the MPG results. Some city/highway, slight upgrade, Computer 24.6 Calculated 25.

    Second day: Computer: 26.9 Calculated 27.4
    Another Tank, lot of down grade: Computer 28 Calculated 29

    Don't know if I believe the calculated, tried to fully fill the tank, but wow.

    Full highway driving really helps the MPG on the 28MPG case used cruise 74mph but some segments of highway at 68 due to 65 speed limit.

    All on mid-grade gas. More later. Very happy with these numbers, plus great ride, comfy seats.

    Cheers,
    Gary
  • I hope someone might be able to help me out. I've got a 2000 Grand Prix GT, and I can't get anything higher than 20 MPG (combined) on regular gas. The car cruises (75-85 mph) between 2500 and 3000 RPM. Any ideas?
  • gxpjoeypgxpjoeyp Posts: 38
    OK CAN I HEAR SOME GP GXP OWNERS' BEST GAS MILEAGE REPORTS,I HAVE 3400 MILES ON MY 06 AND THE BEST I HAVE GOTTEN THUS FAR IS 20.2 MPG WITH 80/20 HWY/CITY.I KEEP HEARIN PEOPLE SAY ITS GOTTA GET BROKE IN,WELL IF 3400 MILES ISNT BROKEN IN THEN I FEEL LIKE TRADIN IT IN,THAT 28 MPG ON THE HIGHWAY IS SO FAR A BAD EST. BY THE EPA,I THINK....

    GXPJOEYP FROM WI
  • tlaurotlauro Posts: 504
    I only have 5k miles on mine but can say in the suburbs/city the mpg reality is horrible. There I average 13-16mpg depending on how I driver her. On the highway, much better.

    I've taken a few 2-3 hour trips to see family. My overall average then has been 24-26mpg. Mostly highway of course, but sitting at even a few lights and going around town once I get to my destination really hurts.

    Honestly, I budget my gas money on 15mpg, perhaps you can use 18 or 19 and be safe.
  • Joeyp,
    Sorry to hear about your mileage. My recent long trip got anywhere from 25-27.8 MPG depending on hills/flat terrain on mid-grade gas. Mostly doing cruise 73-75 with ac. Also think I got 28.5, but not sure on an all hwy down hill segment. Am seeing 21-22 hwy/city mix to work. But if I play with the throttle then it is easy to get 17-18. I find that cruise works much better than my best at having a light foot. Have seen an improvement sometime between 2500-5000 miles, currently have 5500.

    Cheers,
    Gary
  • gxpjoeypgxpjoeyp Posts: 38
    Thanks Bubbaman,now is the mpg your reporting according to the numbers on the dash computer or are they according to you figuring out the mpg with a calculator after your trip and you have refilled your tank? I guess what i will do is filler up and jump on I-43,I live in milwaukee, AND TAKE A DRIVE TO GREEN BAY(NOT TO SEE THE PACKERS THATS FOR SURE)I should be able to put 150 or so miles on that trip and that highway is nice and flat all the way,so i should hopefully see what you go up to 27 mpg if i got that at 70-75 i would be really satisfied....O YEA GO STEELERS!!!!

    GXP JOEYP
  • It is really both. I reset the computer each time and compare actual (calculated) to the computer, most of the time they are close (within .5 mpg) usually a little low, sometimes higher. I calculated a 28.5 MPG and computer said 27.1, so I don't believe I fully got the gas in on the calculated. My latest computer week of work 15miles each way, 10 miles hwy, 5 city is 21.9. I mostly use cruise on the freeway since I am not really awake at times or just dont' want to get a ticket, something easy in the GXP. Let me know if your mileage improves.

    Shamefully a Cowboys fan,
    Gary
  • gxpjoeypgxpjoeyp Posts: 38
    HI ALL I JUST SEEN THE WINDOW STICKER FOR THE 07 GP GXP, BASE PRICE IS UP MORE THAN $1,000.00 XM IS DOWN FROM THE 06 PRICE OF 385.00 TO 199.00,AND THE THING THAT CAUGHT MY EYE THE MOST IS THE EPA MPG 2006 WAS EST AT 17/CITY 28/HWY...THE 07 IS 17/25 3 MPG LESS THAN THE 06,HUGE DIFFRENCE IN MY EYES A FAR AS EST GO.I HAVE 4200 MILES ON MY 06 AND STILL HAVENT CRACKED 21 MPG WITH 85% HWY DRIVIN...JUST MY 2 CENTS

    GXPJOEYP
  • I thought that EPA estimates were going to get tougher this next year for all cars, expect them to go down for all. Is it 07 or 08 they were going to change.

    Question, I got 26/27 on my all highway trips using mid-grade. What I have seen in the city/hwy mix is that different grades of gas matters. I have averaged 19-20.5 for regular. 20.9-21.5 for mid-grade and 21.9-23 for premium mix city/hwy. I use cruise on the freeway since the cutoff to 4 cyl is done much better buy the computer over my foot.

    Hope this helps,
    Cheers,
    Gary
  • gxpjoeypgxpjoeyp Posts: 38
    Maybe the gas in wisconsin is lousy I dont know but I do know that I have always used premium/93 octane since the car was new,do the cruise thing on the xpway,dont hammer the hell out of it, who knows,but here in milwaukee we use that re formulated gas more expensive cause it burns cleaner so they say 75 miles north of me they use the "old" gas....GO STEELERS!!!!!

    GXPJOEYP
  • Interesting, noticed when the summer formulation, aka, more ethanol came out mileage dropped a little. But this weeks tank is 22.0 on premium. What is your total miles, mine is at 5600.

    Deep in the heart of Texas,

    Go Cowboys,

    Cheers,
    Gary
  • gxpjoeypgxpjoeyp Posts: 38
    WELL THE COWBOYS @#$%^^&& HA HA HA 1ST AND FOREMOST, AND I GOT 4300 MILES ON MY 06
  • ocmike3ocmike3 Posts: 232
    I've only got about 4400 miles on my 2005 GXP. My last road trip was cruising 65mph +/- a couple mph and the 5.3L DOD returned 27.6mpg (232 miles @ 8.4 gallons premium) running the A/C for a good portion of the trip.
    I know during the winter months we have to run 10% ethanol and my mileage drops by 10 -15%.
    I do know if I let my foot control the throttle the mileage isn't nearly as good. ;)
  • rmozolrmozol Posts: 124
    I finally got an out of town trip, to check mileage. I filled in the city and headed out. For a 123 mile trip one-way, I got a measured 26.1, with 27.0 DIC. This included a couple of traffic jams, with stop and go. I used the cruise between 70 - 72. I was in a wedding procession with some 69 - 70 GTO Judges, so hit it a few times and did some burners! It dropped to 20 something (DIC) after this city driving and gas useage. Others heard this thing coming down the street too. I thought it was just loud from behind, but I guess not! On the way home, I got a measured 26.5, with 27.8 DIC. I used premium, and a light throttle to get up to speed. I only have 2436 miles on it too. I'm content with this mileage.
  • blckthreeblckthree Posts: 153
    I sure don't know how you got 26/27 on the highway, wish I could. Only time I came close to that was one day on some flat highway with a tail wind, got 25, never seen it since.

    My average highway speed is about 80mph, give or take a bit. Average mpg is about 21-22. Not bad for 80mph, but not what I had hoped for. I won't complain, it is still a nice ride and cheaper to feed than the old Yukon was.

    Just over 13000 miles now, no troubles except for an OnStar module going out. Didn't bother me, except that it had some message every time you started the car. Got tired of the car talking to me.

    Mike
  • rayainswrayainsw Posts: 2,476
    "THE 07 IS 17/25 3 MPG LESS THAN THE 06"

    I have not been to my dealer since 2007s started arriving.
    Was this the sticker on a car - or "Click Here For Window Sticker" on GMBuypower or Pontiac's web site?
    ( These are often wrong. )

    The EPA website shows the 2007 as 18 \ 27 ( 21 combined )

    http://www.fueleconomy.gov/feg/findacar.htm

    And on the Pontiac web site, at the beginning step of "Build Your " - it shows 17 \ 28 for the GXP.
    Odd.....

    - Ray
    With much experience & many thoughts on MPG . . .
  • rayainswrayainsw Posts: 2,476
    My gas mileage is “fine”.

    Details:

    First – highway MPG: I have achieved over 22 MPG for a full tank only a few times in over 19,000 miles. They were close to ‘ideal’ “real-world” conditions.

    ‘Ideal’ “real-world” conditions - probably sounds like an oxymoron, but what I mean is: In the “real-world”, I am NOT constrained by the EPA test limits on rate of acceleration when I merge or pass or leave a traffic light. In the real world, roads have at least some traffic and I am constrained largely [ on Interstates ] by local speed enforcement rather than EPA test max speed (still 60 MPH!!) and I am free to drive with my A/C on. ‘Ideal’ conditions mean relatively light traffic, cool enough ambient temps to be comfortable without the A/C compressor running, cool enough that the air entering the motor is relatively dense, and mostly running on roads with little significant elevation change. And only me in the car, and no more than a weekend case.

    My overall fuel mileage likely now stands at close to 19.0. But if I remove a few of the ‘best’ tanks ( not typical ) from the equation, the average probably drops closer to 18.5.

    Second, I am satisfied with the overall fuel mileage, given the available performance & how often I utilize it. (Many smiles per gallon, thank you.)

    My “around town” MPG reflects the fact that I really enjoy the V8’s acceleration – feel & sound. And I use it whenever I (safely) can. And I use all of it. WOT. Often. Thus I do not achieve the EPA estimate there. No big surprise.

    [ The GXP’s acceleration is really the one dynamic performance aspect where I feel like I can legally and safely utilize 100% of the available performance = HP & TQ on public roads. Perhaps not for long at any given time, as more than 10 or 15 seconds of WOT, in second gear, will have this car moving faster than any open road speed limit in the US. But compared to lateral acceleration & braking, it is a thrill that I can regularly enjoy, asking it to deliver absolutely all the power that it has to give. In cornering, for example, I always try to leave significant margin for the unexpected & unpredictable – sand or oil or water across an apex, or another driver doing something ill advised. Acceleration is something that I can enjoy - every time I drive my GXP! ]

    Although I have seen (and quoted here) that GM states DoD can function at up to 80 MPH under absolutely ideal conditions, my feeling is that in the real world, the slightest headwind, acceleration to pass, or uphill incline, etc. will result in DoD = off.

    And the point in the fuel mileage vs MPH curve where above a certain MPH, under certain specific conditions, DoD will not engage - likely results in a sharp drop in MPG. In fact, I’d predict that it will result in a discontinuity (??) in the curve. Meaning a straight drop, where DoD disengages, then a continuation of the downward sloping curve – at a substantially lower MPG level as speed continues to rise.

    For example. One might expect a somewhat linear drop in MPG as speed rises across the range of typical US highway travel. (Yes, I know, not really linear and not over all speed ranges, etc)

    But for purposes of illustration here - If I assume that at an absolutely steady speed of 60 MPH, my GXP can achieve 30 MPG, then at 65 it might be capable of 28 and at 70 it might be 26 and at 75 it might be 24 and at 80 it might be 22 and at 85 MPH, 20 MPG.

    If DoD is operable up to 70, but will not engage starting at say 73.14159 MPH for instance, the numbers might then look like this:

    MPH\MPG

    60 – 30 (DoD on)
    65 – 28 (DoD on)
    70 – 26 (DoD on)
    75 – 20 (No DoD - instead of 24)
    80 – 18 (No DoD - instead of 22)

    I am making these numbers up, but I believe they are in the range of possibility \ reality for my GXP.

    This would mean that exceeding the DoD engagement threshold would cost something like an additional 20 or more percent (24 with DoD vs. 20 at 75 MPH without DoD and 22 vs. 18 at 80, etc.) beyond the expected decrease as speed rises beyond whatever that critical speed actually is. My driving suggests that the threshold speed ( above this, DoD does not engage in ** my ** typical driving ) is between 70 and 75.

    But that’s just me speculating.

    YMMV.

    - Ray
    Still enjoying the drive – and not obsessing about MPG . . (?)
  • ocmike3ocmike3 Posts: 232
    I think the key is being able to set the cruise and let it go... I do know when I run 75-85mph I notice that the DOD doesn't kick in nearly as often as 65-75mph. I know on a couple of tanks where it was mixed city with on-off freeway romps, my GXP was lucky to get 18mpg.
  • chats1chats1 Posts: 158
    Hi! I have 15,500 miles on my 2006 GXP which I purchased last August. Car has run great and I have gotten up to 28.7 on it. Mostly highway driving. Used it alot in August going down to the Jersey Shore and the mileage was great. Can't complain at all. Chats1
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